1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more specifically to an illumination method of removing moire phenomenon in a reflective type LCD assembly that minimizes moire phenomena and light leakage, which are frequently generated in the reflective type LCD assembly, without display performance degradation, and a reflective type LCD assembly using the same. A light supply unit for assembly, and a method of fabricating a light distribution alteration unit thereof are also disclosed.
2. Description of the Related Art
Generally, an LCD is one kind of flat panel displays precisely. LCD controls an electro-optical property of liquid crystal to display an image and converts image data of electric signals to a picture that a user can recognize.
In order to perform an improved display operation through the LCD, it is very important to control both material characteristic and optical characteristic of the liquid crystal. However, in view of the fact that the liquid crystal is a light receiving device, it is also very important to efficiently use a light source which is supplied to the liquid crystal.
In case there is not provided the light source, or the light source is not efficiently used, even the precisely controlled liquid crystal of the LCD cannot allow the user to recognize any data through the LCD.
According to the use of the light source, LCDs are classified into a reflective type LCD in which the display operation is performed using an external light source, and a backlight LCD in which light is generated using its own charged energy and the display operation is performed using the light.
The reflective type LCD that displays images using only the light from the external light source consumes much less power compared to the backlight LCD. However, without external light source, the user cannot recognize the display.
This is a fatal disadvantage in a display device if the device cannot operate in any conditions or environments.
To solve the problem, there has been provided an improved reflective type LCD assembly that, if the light is insufficiently supplied from the external light, generates additional lights to normally perform the display operation, thereby having advantages of both the reflective type LCD and the backlight LCD.
In order to achieve an improved reflective type LCD assembly 100, as shown in FIGS. 1 and 2, an LCD 10 in which the liquid crystal is controlled to adjust an optical transmittance and a light supply unit 20 that supplies the light to the LCD 10 with small power consumption are necessary.
At this time, the light supply unit 20 has a light source 21 and first and second optical members 25 and 27 for uniformly supplying the light generated from the light source 21 to the LCD 10.
More particularly, a point light source type of light emitting diode (LED) with a power consumption of only a few to a few tens mW is mostly served as the light source 21.
By using the point light source type LED, the power consumption can be remarkably reduced.
However, if the LED is directly applied to a desired portion of the LCD 10, some parts of the LCD 10, which are near to the LED, are bright, but other parts, which are far from the point light source, are dark. In other words, the luminance difference in a display screen degrades the display performance of the LCD.
In order to cure the non-uniform luminance problem of the LED as described above, the first optical member 25 and the second optical member 27 are necessary to indirectly transform the light generated from the point light source type LED into the planar light.
The first optical member 25 and the second optical member 27 transform the light from the point light source type LED into the linear light, and then the linear light into the planar light.
Particularly, the first optical member 27 has a desired length to transform the point light source into the linear light source type. The first optical member 27 is formed into a square rod, and provided with the point light source at an end thereof.
As shown in FIG. 1, the first optical member 27 irradiates the light in an angle of 2.
The linear light source formed by the first optical member 27 should be transformed into the planar light source. However, in order to achieve the planar light source, a complicated optical mechanism is required.
As shown in FIGS. 1 and 2, the light irradiated from the first optical member 27, which has a light distribution in the linear light source, is transferred to the second optical member 25 in the form of a square plate. On an upper portion of the second optical member 25, there is formed a sawtooth-shape light reflective pattern 25a. 
At this time, the light coming from the first optical member 27 is uniformly transferred from a front portion 25b of the light reflective pattern 25a, which is adjacent to the first optical member 27, to a rear portion 25c of the light reflective pattern 25a. 
Therefore, the light irradiated from the first optical member 27 is transformed into the light having the light distribution in the planar light source.
The planar light transformed by the second optical member 25 is then incident onto the reflective type LCD 10.
Then, the incident light on the reflective type LCD 10 is reflected by a reflective electrode 15 which is formed in the reflective type LCD 10 in the form of a matrix, and is passed again through the second optical member 25, and is then incident on user's eyes so that the user can visually recognize desired information.
The improved reflective type LCD assembly 100 can display images even in a dark place.
The light reflective pattern 25a that provides planar light source, overlaps with the reflective electrode 15 formed in the LCD 10. If two patterns are overlapped each other as described above, a moire pattern may be generated, degrading the display performance.
To solve the problem, an aligning angle between the light reflective pattern 25a and the reflective electrode 15 has been changed to avoid parallel alignment of each other but to form a cross alignment.
At this time, when the aligning angle between the light reflective pattern 25a and the reflective electrode 15 is about 22.5°, as shown in FIG. 2, the moire phenomenon is the least generated.
However, even though the light reflective pattern 25a and the reflective electrode 15 are aligned to cross each other, narrower pitches of the light reflective pattern 25a and the reflective electrode 15 may generate the moire phenomenon again.
To this end, the moire phenomenon is not a problem in a conventional mid and small-sized LCD having low resolution. However, in a large-sized LCD, the narrow pitches of the light reflective pattern 25a and the reflective electrode 15 generate the moire phenomenon again.
Further, if the light reflective pattern 25a and the reflective electrode 15 are tilted at a desired angle, e.g., 22.5°, only a half of the light reflected by the light reflective pattern 25a goes to the reflective electrode 15, and the rest of the light goes to an undesired place by the tilted light reflective pattern 25a. Therefore, there is another problem that an entire luminance of the reflective type LCD assembly is lowered, and a power consumption of the assembly is thus increased.
Recently, to solve the problem, it was attempted to conform the pitch of the light reflective pattern 25a to the pitch of the reflective electrode 15, thereby reducing the moire.
However, if the pitch of the reflective electrode 15 changes, the light reflective pattern 25a should be re-fabricated. Further, if the light reflective pattern 25a and the reflective electrode 15 do not align correctly, it creates the moire again, and lowers the display. In this case, the power consumption also increases because of the low luminance.